The mobile phone industry has had an enormous development both regarding quality of service and transmission capabilities, as well as the technology for producing advanced communications terminals. In only a couple of decades the communication systems have gone from analogue to digital, and at the same time the dimensions of the communication terminals have gone from briefcase size to the pocket size phones of today. Still today, mobile phones are getting smaller and smaller and the size is generally considered to be an important factor for the end customer: The development in electronics has made it possible to miniaturize the components of the terminals, at the same time making the terminals capable of performing more advanced functions and services. The development of new transmission schemes, the so-called 3rd generation mobile system standing at the door and the 4th generation to be expected maybe ten years later, also provides the possibility to convey more advanced data to the wireless communication terminals, such as real time video.
In order to benefit from the capabilities of the transmission system, the future generation of phones will have a large display in order to perform multimedia input and output, and the picture quality will be of high importance. Still, the keypad or keyboard must be large enough to allow people to press one key at a time.
FIG. 1 discloses a typical example of a state of the art mobile phone or communication terminal 1, carried by a housing or chassis 2. The size of a keypad 4 and a display 3 basically sets the limit of how small the terminal 1 can be. However, to be able to work as a standard phone for voice interaction, the terminal 1 also includes a microphone 5 and a speaker 6, preferably arranged at opposite ends of the terminal 1. FIG. 3 discloses a different embodiment of a state of the art communication terminal 1, wherein the display 3 occupies a larger portion of the front side of the terminal. Several of the functions of the keypad 4 have been included in a graphical user interface applicable to the display 3, rendering a data input interface having less keys. Those keys 4 may also be moved to the side of the communication terminal in order to allow for the display 3 to occupy a larger portion of the front side of terminal 1. A specific tool 8 may be provided for inputting data on a touch-sensitive screen of the display 3. FIGS. 1 and 3 show two typical examples of state of the art communication terminals 1, whereas the skilled persons will realize that combinations of the two are also well known as well as other designs.
With the development of the communication systems and the capabilities of multimedia functions, the demands on the sound quality from the terminals will also increase. In the next generation of terminals using Wideband Code Division Multiple Access (W-CDMA) technique, it will be possible to user a wider audio frequency band. The speaker of the terminal may also be used as a ringer instead of a traditional buzzer, for a single tone or polyphonic ring signals, and as a hand free speaker built into the phone. Normally, these functions are performed by a second speaker mounted in the back of the phone, but combined speakers for two or all three of these functions exist.
In the state of the art communication terminal a terminal output 7 is mounted on the front of the terminal above the display with the speaker 6 immediately behind the output 7, as shown in FIGS. 1 and 3. This means that even with a smallest available speaker used today, with a diameter of about 13 mm, the terminal would be approximately this much longer in its longitudinal extension than what would have been the case if only the display 3 and/or keypad 4 had defined the length of the terminal 1. The antenna of the terminal is generally located at the upper portion of the backside of the terminal, the lower backside being occupied by a battery. Placing the speaker 6 behind the display 3 would therefore increase the thickness of the terminal 1 since it would have to compete with the antenna for the relevant space.
The performance of the speaker is to a high extent dependent on the back volume, i.e., the acoustic resonance cavity behind the speaker. For best performance, the back volume should be sealed. In a normal case the whole phone is used as a back volume, but it is almost impossible to seal a phone. As mentioned above, almost every phone today has the speaker position in the upper parts of the front of the terminal above the display and keyboard. This means that the height of the speaker, display and the keyboard determines the length of the phone. Since the speaker performances is highly dependent on the dimension, reduction of the speaker size results in less good acoustics. There is also a general desire to have larger displays in the communication terminal, not just wider by also longer, and with the common layout of the keyboard such as disclosed in FIG. 1 and which people are used to, the height of the terminal can basically not be reduced more than today without resulting drawbacks to the display 3 or keypad 4.
A solution to this problem of miniaturization of communication terminals is proposed in WO 00/38475, in which the acoustic resonance chamber of the speaker is completely or partly located in the electromagnetic resonance chamber of the antenna. The use of a single resonance chamber instead of two separate ones makes it possible to manufacture smaller communication devices. According to the proposed solutions the speaker is placed outside the resonance chamber, the backside of the speaker being connected to the resonance chamber by at least one acoustic channel. However, the arrangement of the speaker beside the resonance chamber has some drawbacks. First of all the acoustic channel has to be properly sealed. Furthermore, the speaker and chamber will both add to the thickness of the terminal, and at the same time the height of the speaker will contribute to the length of the terminal.